It is important to coordinate time related information across time-synchronized data processing systems in an effort to maintain synchronization of this information across all systems in a timing network without requiring dedicated connections amongst systems with those connections being used exclusively for timing. This time related information includes things such as: a Coordinated Time Network Identifier (CTN Id—this specifies the network in which synchronization is occurring), a Primary Reference Time (PRT) Source Identifier (which identifies the time source within the network), Leap Seconds Offset value, local time Information such as Time Zone (TZ) offset and Daylight Savings Time (DST) offset, and timing network configuration information. The present invention provides a means to accomplish this in an improved fashion when compared to current solutions.
In today's data processing network environments, it is extremely desirable to be able to make changes to any of this time related information at the same “instant” on all of the systems in a timing network. In order to maintain the coordination of these time parameters across the network, current solutions do not provide a means for a timing network node to lose communication with a clock source temporarily and to still guarantee that the timing system parameter information is still valid.
One of the systems that is used to provide timing synchronization and coordination of timing parameters used in synchronization is the IBM 9037 Sysplex Timer or ETR (External Time Reference). In this system the data processing systems in the network have a dedicated direct connection to the 9037 Sysplex Timer for the sole purpose of forwarding timing information to that system. In this system, directly attached data processing components continually monitor each individual timing related information field to determine if it has been updated. This involves the consumption of additional processing power at each node in the network to detect changes in the timing parameters. The timing information includes an ETR network identifier, the leap seconds offset and the total time offset, which is the sum of the time zone and daylight savings time offsets. Scheduled updates are viewed at the ETR console and not at each individual system in the timing network. Lastly, if a node loses all communication with the ETR, the parameter data is considered to be invalid at that point in time.
Another known approach to timing in networked systems is provided by the standard Network Timing Protocol (NTP) defined in RFC 1305. In general, except for a network identifier, the leap seconds offset, and a time source identifier, additional network parameter information is propagated throughout the network in specialized control messages that are separate from the actual time synchronization messages. Because the update is broadcast throughout the network once it has happened, the synchronization of when the updates occur across the network is subject to network delays which increase with distance between network nodes. Furthermore, the Network Timing Protocol is generic in that it is intended to be independent of the hardware on which it is employed.